/**
  * deletes an object from database
  * @param int contentid
  */
 public static function delete_by_id($content_id)
 {
     Logger::log("Enter: CNContent::delete_by_id()");
     // soft deleting
     ModerationQueue::remove_content($content_id);
     CNContent::update_content_status($content_id, DELETED);
     Tag::delete_tags_for_content($content_id);
     Logger::log("Deleting the all comments related to this object");
     Comment::delete_all_comment_of_content($content_id);
     Logger::log("Exit: CNContent::delete_by_id()");
     return;
 }